Piezoelectric vibrator can be used devices for implementing a timer function in electronic devices. As electronic devices are made smaller, there is demand for piezoelectric vibrators to be made smaller as well, and piezoelectric vibrators manufactured using MEMS (Micro Electro Mechanical Systems) technology (called “MEMS vibrators” hereinafter) are garnering attention.
In MEMS vibrators, there are cases where variations in resonant frequencies arise due to manufacturing variations. Additional etching or the like is therefore carried out during or after the manufacture of the MEMS vibrator in order to adjust the frequency thereof.
For example, Patent Document 1 discloses a configuration that adjusts a resonant frequency by forming an additional film constituted of a single material on an electrode of a piezoelectric vibrator and then causing the thickness of the additional film in a first region to differ from the thickness of the additional film in a second region.
Additionally, for example, Patent Document 2 discloses a configuration that adjusts a resonant frequency in a vibrator having a plurality of vibrating arms by reducing rough adjustment mass parts provided on tip sides of the vibrating arms and reducing fine adjustment mass parts provided on base end sides of the vibrating arms.    Patent Document 1: Japanese Patent No. 4930381 specification.    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2012-065293.
As described above, according to the configuration disclosed in Patent Document 1, the additional film for adjusting the resonant frequency is formed from a single material. To achieve different thicknesses in the additional film from region to region, it is therefore necessary to carry out an adjustment operation, such as irradiation with a beam, on each region, which is inefficient.
According to the configuration disclosed in Patent Document 2 as well, it is necessary to remove the rough adjustment mass parts provided on the tip sides of the vibrating arms and remove the fine adjustment mass parts provided on the base end sides of the vibrating arms individually, which is inefficient.